Shaft seal means



United States Patent lnventor George V. Woodllng 22077 W. Lake Road,Rocky River, Ohio 44116 Appl. No. 734,669 Filed June 5, 1968 PatentedNov. 24, 1970 SHAFT SEAL MEANS 13 Claims, 6 Drawing Figs.

US. Cl. 277/ 172, 277/207 Int. Cl. Fl6j 9/00; F 1 6k 41/00 277/172,

FleldofSearch .1

{56] References Cited UNITED STATES PATENTS 3,088,442 5/1963 Selfet a1277/173X 3,184,247 5/1965 Leutwyler. 277/170 3,421,412 1/1969 Ackley277/95 Primary ExaminerSamuel Rothberg Attorney-Woodling, Krost, Grangerand Rust ABSTRACT: A fluid seal for a shaft mounted in an annular groovesurrounding the shaft. The fluid seal comprises an O- ring of rubberlikematerial having substantially a square cross section with four raisedcrown corners. Three of the crown corners sealingly engage the groovewith only one sealingly engaging the shaft which reduces the frictionand the resultant j amount of heat generated.

Patented Nov. 24, 1970 3: -J INVENTOR. 2a 30 3| BY GEORGE vwooouws SHAFTSEA L MEANS My invention relates in general to shaft fluid seals andmore particularly to rotatingshaft seals. 1

Although my invention is particularly useful for rotating shaft seals,it isnot necessarily limited thereto, because is it may also be used forreciprocating shaft seals or in other situations.

Most elastomers, suchasrubberlilte O-rings, when heated in a stretchedor stressed (garterlike) condition, will contract.

This contraction (shrinkage) is damaging because it results in atendency for the O-ring to squeeze all the harder against the rotatingshaft, which self-perpetuates more heat. Continued rotation of the shafttends to cause the O-ring to seize'the shaft, whereupon more frictionwill cause more heat and the process becomes self-perpetuating until theO-ring is destroyed. This phenomenon is known as the GQW-JOULE effect.

An object of my invention is to resist heat shrinkage of an O-ring abouta shaft.

Another object is to' minimize the phenomenon, known as the GOW-JOULEeffect.

Another objectis to provide a narrow axial contact engagement betweenthe O-ring and the shaft.

Another object is the provision of mounting an O-ring in an inclinedgroove extending outwardly from the shaft bore.

Another object is to withdraw the O-ring from the shaft as it iscompressed by fluid pressure into the inclined groove.

Another object is to withdraw the O-ring from the shaft at a slower ratethan it is compressed into the groove.

Another object is the provision of an inclined groove having a sidewalloverlaying a portion of the O-ring.

Another object is the provision of an inclined groove having a sidewall,defining with the shaft bore, an annular apex pointing in a directionopposite to that at which the fluid pressure is applied to the O-ring.

Another object is the provision of a takeup apex void 'at the terminalend of the annular apex, whereby the O-ring is required to fill up thetakeup apex void before it can start to extrude between the shaft andthe bore.

Another object is the provision of an inclined groove which accommodateseither the round type of O-ring in cross section or the square typeofO-ring in cross section.

Another object is a-shaft seal having a large cushion effect and a smallfrictional contact with the shaft.

Another object is the provision of an inclined groove for an O-ringwhich does not necessarily require close machining tolerances.

Other objects and a fuller understanding of this invention may be had byreferring to the following description and claims, taken in conjunctionwith the accompanyingdrawings, in which:

FIG. 1 is a view, diagrammatically illustrating the position in whichmyshaft seal may be mounted between a shaft and a cylindrical surfaceeounterbore confronting and spaced outwardly from the shaft;

FIG. 2 is an end view of the shaft seal only of FIG. 1 looking in thedirection of the line 2-2;

FIG. 3 is an enlarged i diametrical, cross-sectional view of a shaftseal (drawn to-substantially three-times scale for a I" shaft) embodyingthe features of my invention and showing an O-ring having substantiallya round cross section;

FIG. 4 is an enlarged fragmentary view of FIG 3, showing therelationship of the round-section O-ring with the inclined groove andthe shaft;

FIG. 5 is a view similar to FIG. 3, but showing a square-section O-ring;and

FIG. 6 is an enlarged fragmentary view of FIG. 5., showing therelationship of the square-section O-ring with the inclined groove andshaft.

In FIGS. -1 and 2, my shaft seal (diagrammatically illustrated) isidentified by the reference character 10, and is to fluid, underpressure in the fluid pressure device, and the direction at which-thepressure is applied against the shaft seal is indicated by the arrows inFIG. 1.

As shown in FIG. 3, my shaftseal assembly comprises a continuous annularbody13 surrounding the shaft 11, and a continuous annular O-ring 14(round cross section) for effecting a fluid seal between the shaft andthe surrounding body. The annular body 13 is preferably made of metaland may be sealingly pressed into the counterbore 12. To this end, theouter cylindrical surface of the surrounding body 13 is provided with anexternal annular groove 15 for receiving an O- ring 16 which makes asealing engagement between the annular body 13 and the counter-bore 12.The O-rings l4 and 16 are preferably composed of rubberlike material,commercially available in various formulations and hardness. For ease inco mounting, the diametrical clearance 17 between the annular body andthe counterbore may reside (depending upon the fluid pressure) in arange from approximately .002 to .008 inch, whereby the O-ring 16 mayact as a cushion, within the limits of the diametrical clearance, toaccommodate for axial eccentricity of the shaft 11. With this cushioneffect, the shaft sealing O-ring 14 is substantially free from beingsubjected to a side thrust due'to eccentricity.

As shown in FIG. 3, the surrounding annular body 13 has a shaft bore 18through which the shaft 11 extends. The diamet: rical shaft clearance 19between the shaft bore 18 and the shaft 11 may reside (depending uponthe fluid pressure) in a range from approximately .004 to .012 inch,being kept as small as possible to prevent the extrusion of the O-ring14 along the shaft 11.

The shaft seal O-ring 14 is disposed to be mounted in an inclined groove24 extending outwardly from the shaftbore 18. As illustrated in FIG. 4,the inclined groove 24 is defined by first and second opposed sidewalls25 and 26 and a bottom wall 27, with the shaft sealing O-ring l4sealingly compressed between the shaft 11 and the inclined groove 24.The first and second opposed sidewalls 25 and 26 respectively extend inthe same general direction and respectively are disposed at an acuteangle to the axis of the shaft bore. The first sidewall 25, which is theshort side, axially overlays a portion ofthe sealing O-ring l4 and thesecond sidewall 26, which is the long side, axially confronts therotating shaft II. The second sidewall 26 terminates into an abutmentend wall 23 for holding the O- ring into the groove.

The included angle of the groove 24 with respect to the shaft bore ispreferably about 15 and may reside in a range from approximately '10 to30. The inclined groove is easily machinableand does not necessarilyrequire close machining tolerances.

The first sidewall 25 and the shaft bore 18 define a substantiallyannular apex 28 which points in a direction opposite to I that at whichthe fluid pressure is applied to the sealing O-ring 14. The annular apex28-has an annular terminating end wall 29 facing in a direction oppositeto which fluid pressure is applied to the sealing O-ring 14. Theterminating end wall 29 provides an apex takeup void 30 between thesealing O-ring 14 and the shaft 11, whereby the O-ring 14 is required tofill up the apex takeup void 30 before it can start to extrude betweenthe shaft and the bore. The width of the inclined groove 24 between theopposing sidewalls 25 and 26 is preferably slightly less that than thewidth of the sealing O-ring to provide a compression side squeeze on theO-ring. The walls of the inclined groove are disposed to support theO-ring 14 in the groove with the O-ring making a five-point engagement(annular surface portion) with the groove and the shaft. The sealingengagement (annular surface portion) of the O- ring 14 with the shaft isat 31 and the sealing engagement with the groove is at 32, 33, 34 and35. In this supported position of the O-ring 14, theshaft engagement at31 is in advance of the annular apex 28; the groove engagement at 32 isagainst the first sidewall 25; the groove engagement at 33 is againstthe bottom wall '27; the groove engagement 34 is against the second side26; and the groove engagement 35 is against the abutment endwall 23.-The groove engagements 32 and 34 are substantially diametricallyopposite each other and the shaft engagement 31 is substantiallydiametrically opposite the center of the O-ring 14. As fluid pressureincreases, the O-ring 14 is compressed down into the inclined groove,filling up the corner takeup voids 36 and 3.7. This downward movement ofthe O-ring 14 functions to withdraw the shaft engagement at 31 radiallyaway from the shaft. Consequently, the more the fluid pressure the lessthe friction area at the shaft engagement 31, resulting in less ,heat.With a 15 inclined groove, a downward movement (one unit) of the centerof the O-ring 14 will tend to withdraw O-ring 14 from the shaft in aradial direction at the shaftengagement 31', a distance of approximately.250 unit, whereby'the withdrawal movement is about one-fourth thecompression movement of the O-ring into the inclined groove; Thus, fluidpressure which is considered to be a disadvantage is converted into anadvantage. As a result, my shaft seal will withstand high fluidpressures, and since the friction area is small, it will also withstandhigh rotating shaft speeds. It is also to be noted that, since the firstsidewall axially overlays a portion of the O-ring 14, it is preventedfrom seizing the shaft. Thus, the GOW-JOULE effect is impeded orminimized, which prolongs the life of the O-rin g. There is anotheradvantage derived from my inclined groove, and that is, as the O-ring 14is compressed by fluid pressure into the bottom of the groove, theO-ring material in the vicinity of the apex takeup void '30 is caused toflow toward the corner takeup voids 36 and 37, and as a result there islittle tendency for the O-ring material to fill up the apex takeup voiduntil the corner takeup voids 36 and 37 are filled up. Any tendency forthe O-ring 14 to extrude between the shaft and the shaft bore lSisdelayed.

For a rotating shaft seal, experience teaches that it is desireable touse the Oring with the smallest cross-sectional diameter, available forthe size ofthe shaft required. Thus, for rotary shaft seals, the largercross-sectional diameter O-rings are generally not used. Usually, thethree smallest commercially available cross-sectional diameters areused; namely, .070 inch, .103 inch and .139 inch, depending upon theshaft speed, measured in feet per minute. For low speeds below 200 feetper minute, the cross-sectional diameter is usually not critical. Forspeeds between 200 to 400 feet per minute, the .139-inch diameter ispreferable; between 200 to 600 feet per minute, the .l03-inch diameteris recommended, and between 200 to 1,500 feet per minute, the .070-inchdiameter is essential. The purpose of using the smaller cross-sectionaldiameter O-rings is to keep the area of axial contact which the O-ringmakes with the shaft as small as possible toreduce friction and theresultant heat generated. For a given amount of squeeze (pressure ofO-ring against the shaft) the area of axial contact is a function of theradius of curvature of the O-ring. For example, the smaller the radiusof curvature, the smaller the area of axial contact, assuming all otherfactors being equal.

Beside the radius of curvature, there is another dimensional factorwhich affects the area of axial contact; namely, the radial thickness ofthe O-ring. The larger the radial thickness of the O-ring, the less therequirement of accurate machining of the O-ring groove. Thus, forexample, a machine tolerance of .003 inch where the O-ring engages thesecond sidewall 26 of the machined groove will not necessarily reflectthe same variation where the O-ring engages the shaft, because with athick O-ring (radial 'dimension) some of the machine tolerance has anopportunity of being absorbed (cushion effect) before it reaches theshaft. Thus, a round cross section O-ring has conflictingcharacteristics; in that, when a small cross section is used to reducethe width of the frictional engagement with the shaft, the radialthickness, of necessity, is small and this precludes the cushion effectwhich is desirable to absorb machine tolerances before it reaches theshaft. The conflicting characteristics may be overcome in FIGS. 5 and 6where a square-section O-ring 40 is mounted in my inclined grooveinstead of a round-section O-ring. The square-section O-ring 40 (usuallyreferred to as a Quad-ring" has the distinction, when mounted in myinclined groove, of providing a small radius of curvature in'contactwith-the shaft and at the same time of providing a'thick radialdimension between the second sidewall 26 of the machined groove and theshaft. Thus, with a square-section O-ring, the inclined groove does notnecessarily require close machining tolerances.

As illustrated in FlG. 6, the square-section O-ring 40, preferablycomposed of rubberlike material, has four crown corners and they make asealing engagement (annular surface portion. with the shaft at 45 andwith the inclined groove at 46, 47 (both crown corners), 48 (both crowncorners) and 49. Thus, the square-section O-ring 40 has at least fiveannular surface portions sealingly engaging the shaft and the inclinedgroove. The frictional contact at 45 with the shaft is relatively smalland thus the friction is small relative to that for a roundsectionO-ring. in FIGS. 3 and 4, the round-section O-ring. in order to providea minimum of friction, may have a cross-sectional diameter ofapproximately .070 inch, or a radius of curvature of approximately .035inch. The crown corners for the square-section O-ring may have a radiusof curvature of approximately .025 inch and a distance of approximately.090 inch and a distance between the centers of the crown corners. Acomparison indicatesfthat the square-section O-ring has less shaftfriction than the round-section O-ring and has approximately twice theradial dimension (cushion effect) between the second side 26 of thegroove and the shaft. Under most operating conditions, whatever theround section O-ring can do, the square-section O-ring in my inclinedgroove can do better.

The square-section O-ring in the vicinity of the apex-take void 30 isnaturally formed inwardly, whereby there is less tendency for thesquare-section O-ring to extrude between the shaft and the shaft bore.The operation of the square-section O-ring follows generally theoperation of the round-section O- ring, except for the differencespointed out above. The squaresection O-ring 40, as it is compressed downin the inclined groove, is radially drawn away from the shaft to reducethe friction the same as the round-section O-ring is drawn away from theshaft.

Although this invention has been described in its preferred form with acertain degree of particularlity, itis understood that the presentdisclosure of the preferred form has been made only by way of exampleand that numerous changes in the details of construction and thecombination and arrangement of parts may be resorted to withoutdeparting from the spirit and the scope of the invention as hereinafterclaimed.

lclaim:

1. Seal means including continuous annular sealing ring means foreffecting a fluid seal between a shaft and a surrounding body, said bodyha'vinga shaft bore through which said shaft extends, said body having agroove extending outwardly from said shaft bore and disposedto receivesaid sealing ring means, said sealing ring means comprising an O-ring ofrubberlike material having at least an annular surface provided withfirst and second raised crown sealing portions spaced apart from eachand including a valley portion therebetween, said first and second crownsealing portions facing in a direction toward said shaft with said firstcrown sealing portion sealingly engaging said shaft, and holding meansfor holding said second crown portion from engaging said shaft.

2. The structure of claim 1, wherein said holding means comprises groovewall means overlying said second crown portion.

3. The structure of claim 1, wherein said O-ring has substantially asquare cross section, and wherein said groove has first andsecondopposed sidewall means and bottom wall means ing end wall meansprovides an apex takeup void between said sealing ring means and saidshaft. 10. The structureoffclaim 3, wherein said bottom wall means isdisposed substantially perpendicular to said first sidewall means.

11. The structure of claim 3, wherein said O-ring has first, second,third and fourth crown corners, with said first crown corner sealinglyengaging said shaft and with said second, third and fourth crown cornerssealingly engaging said groove.

12. The structure of claim 3, wherein said sealing ring means withdrawsin a radial direction from said shaft upon a compression movementthereof in said groove toward said bottom wall means.

R3. The structure of claim 12, wherein said radial withdrawal movementis less than said compression movement toward said bottom wall means.

